1. Technical Field
The present invention generally relates to heating systems, and more specifically relates to heating system for umbrella-shaped structures.
2. Related Art
Infrared heaters are well known and have been used for many years in various heating applications. Heating with infrared energy is often more efficient than convective forced air heating systems for several reasons. First, convection heating involves a gas (typically air) or liquid that transfers heat from one solid body to another. Because most convection heating uses air as the medium for transferring the heat, convection can only be controlled by air temperature and air speed. In contrast, infrared heating (which includes waves having wavelengths between about 0.75 microns to about 1000 microns) only heats objects and does not heat the air in space that it travels through. Air, the medium for convective heat, is a poor absorber of infrared heat, thus infrared heat can be transmitted long distances with minimum loss of energy to air. When infrared energy is directed onto an object (such as a person), the energy is converted into heat. The heated object then becomes a heat source that transfers heat into the air surrounding the object.
Because infrared waves travel in a straight line at the speed of light, they can be directed in a specific direction toward a specific object. The distance infrared waves travel is dependent on the type of infrared source and the power of the infrared source. The wavelength of the infrared waves may influence the depth of penetration of the infrared waves into the objects. Infrared waves are typically divided into short, medium and long waves through the infrared wavelength spectrum of about 0.75 to 1000 μm. Short infrared waves generally have the deepest penetration capabilities while long infrared waves have the least penetration capabilities. Infrared heaters may include infrared elements that produce a single or multiple wavelengths depending on the application.
Infrared heating elements are available in a variety of different styles and types. For example, come common style of infrared elements include panel emitters (full trough (FTE), full flat (FFE), have square (HSE), etc.), Edison/light bulb screw-base emitters, and tube emitters. There are also three primary types of infrared elements: ceramic, quartz glass, and metal. A comparison of the three types of infrared elements is shown in Table I.
TABLE ICeramicMetalQuartzResponse TimeSlowSlowFastLongevityExcellentExcellentGoodDurabilityGoodExcellentGoodInfrared Efficiency95%55%60%Controllability withYesNoNoIntegral Thermocouple?Maximum Operating1290° F.1400° F.1600° F. (870° C.)Temperature(700° C.)(750° C.)
Another variable for an infrared element is how the infrared waves are generated. The two primary sources of infrared waves are from electric power and combustion. Those skilled in the art recognize different benefits of electric and combustion infrared generation, such as, for example, efficiency, cost, mobility, maximum temperature, durability, and response time. One example infrared heater, disclosed in U.S. Pat. No. 6,445,623, produces infrared heat by burning propane gas in a combustion chamber. Another infrared heat source is a tungsten halogen high intensity emitter that includes a linear coiled tungsten filament surrounded by a clear quartz glass tube. The addition of a halogen gas to the tube prevents blackening of the tube interior due to evaporation of the tungsten filament. These types of emitters run on electricity and can be configured for a variety of different applications.